var arr = [4, 2, 27];
var arr1 = [1, 3, 6, 9, 3, 6];
// var res = arr.concat(arr1)
// var res = arr1.slice(2, 5)

// var res = arr1.splice(1, 2)
// var res = arr1.splice(1, 0, "zhangsan")
var res = arr1.splice(1, 2, 2, 3)

console.log(res)
console.log(arr1)